The isolation of the tumor-inhibitory principles of Rollinia papillionella, R. sericea, Salacia madagascariensis, Maquira costaricana, and M. calophylla will be pursued using activity guided chromatographic procedures. The structural elucidation of the principles will be achieved using chemical and spectroscopic methods. Derivatives of the active principles will be synthesized in order to examine the structure-activity relationships among each class of compound isolated. In conjunction with this, derivatives of the steganin class of lignans and of the maytansinoids will be synthesized to extend the structure-activity relationships in each series and to provide new derivatives with reduced toxicity and increased activity.